In Situ Encapsulation Kinetics Monitored by Microfluidics

We use microfluidic PDMS devices to monitor the encapsulation process occurring at an emulsion droplet interface which is indicated by the changes in the droplet interfacial deformability. Deformations are induced by constriction chambers at the microfluidic chip. This method allows for a precise measurement of in situ microencapsulation early kinetics (below 0.5 s). We study the formation of polyurea microcapsules (PUMCs). Shell formation occurs at the oil-water interface by an immediate reaction of a di- or multi amine dissolved in the aqueous phase and a diisocyanate dissolved in the oil phase. We are able to address the reactivity of certain reactants on the microencapsulation process. We observe that both monomers of this encapsulation contribute differently which is in contrast to the present understanding of the PUMC formation. In addition, we quantify the retarding effect of the interface stabilizing agent (surfactant) on the encapsulation kinetics. Our approach shows that microfluidics is efficient for monitoring and studying in situ encapsulations up to the potential for the determination of interfacial polymerization kinetics for the generation of microcapsules with well-defined properties and the study of soft reactive interfaces.